^node.selectBool[XPath-query]
This method returns result of XPath-query in the scope of specified node, if it is a Boolean value. If resulted value is not a Boolean, method returns exception of type parser.runtime.
Before using prefixes of name spaces in the query one must define them, see $xdoc.search-namespaces.
Example $d[^xdoc::create{<?xml version="1.0" encoding="windows-1251" ?>
<t attr="hello" n="123"/>}]
^if(^d.selectBool[/t/@n > 10]){
/t/@n greater than 10 }{
not greater }
Detailed specification of XPath is available at: http://www.w3.org/TR/xpath